Background: Frail Veterans are at increased risk for poor surgical outcomes. Although surgical techniques have advanced to a level where surgery on very old adults is feasible, if a patient is also frail, the stress of surgery may overwhelm their adaptive capacities, placing them at increased risk of mortality, morbidity, and institutionalization even if surgery is technically successful. Frailty is a clinical syndrome that is commonly characterized by muscle atrophy, diminished strength and speed, decreased physical activity, and exhaustion. It is independent of any specific disease, but it increases with age and worsens disease prognoses by diminishing capacity to tolerate stressors. Thus, while surgery is often indicated for older patients, frail candidates are less likely than robust counterparts to tolerate the procedure and/or recover functional capacity. In fact, recent VA data demonstrate that frailty is a more powerful predictor of increased perioperative mortality, morbidity, length of stay, and cost than predictions based on age or comorbidity alone. As the Veteran and US populations grow older, frailty will increase, making it critically important to identify effective strategies for improving the surgical recovery and outcomes of frail patients. ?Prehabilitation? has the potential to improve surgical outcomes among the frail. Prior research demonstrates that inter-disciplinary rehabilitation strategies deployed after surgery enhance recovery and improve outcomes by building strength and improving nutrition. Based on this success, there is growing interest in ?prehabilitation?, which is a similar intervention deployed before surgery. By modifying physiological and environmental risks, prehabilitation aims to augment patients' capacity to compensate for the stress of surgery itself and the convalescent period thereafter. Frail patients may benefit disproportionately from prehabilitation because they have diminished capacity to endure the procedure and/or recovery. Preliminary evidence suggests that preoperative exercise interventions improve surgical outcomes. However, prehabilitation has not yet been studied in either Veteran or specifically frail populations, and no prior studies used home-based prehabilitation strategies to safely minimize travel-related barriers to participation. Objectives: We will examine the feasibility of a novel, multifaceted, home-based prehabilitation intervention designed to improve functional capacity and postoperative outcomes for frail Veterans anticipating cardiothoracic surgery. Specific aims are to: (1) Estimate rates of recruitment, retention, and adherence to the intervention; and evaluate participation barriers. (2) Measure changes over time in frailty, physical function, pulmonary function, nutrition, and health-related quality of life at baseline, the day of surgery, and 30 and 90 days after surgery. (3) Explore changes in postoperative mortality, major complications, length of hospital stay, and level of independent living using case-matched historical controls. Methods: This single-arm pilot study will enroll a consecutive cohort of up to 30 Veterans identified as frail using a standardized frailty assessment and scheduled for major cardiothoracic surgery at the VA Pittsburgh Healthcare System. The 4 week long prehabilitation regimen will include: (a) aerobic conditioning, (b) strength and coordination training, (c) respiratory muscle training, and (d) nutritional coaching and supplementation. Pre- and post-prehabilitation assessments will include: (a) frailty; (b) physical function; (c) pulmonary function; (d) nutrition; and (e) health-related quality of life. Postoperative outcomes will include length of stay, mortality and complications. Compliance with the prehabilitation regimen will be assessed through patient logs and pedometers. Analyses will inform a larger randomized controlled trial testing the prehabilitation intervention. Findings will be relevant for the 42,000 frail Veterans scheduled for major elective surgery each year.